基于L-THIA模型的四川省濑溪河流域非点源污染负荷分析

Non-Point Source Pollution Loads Analysis of Laixi River Watershed,Sichuan based on L-THIA Model

非点源污染是造成流域水环境恶化的重要原因之一,掌握非点源污染的时空分布特征是流域水环境污染防治和流域综合管理的基础性工作.为落实国家《水污染防治行动计划》,四川省启动了濑溪河等流域综合治理达标方案编制工作,探明濑溪河流域非点源污染负荷及其分布特征是该方案编制的前提.以四川省境内濑溪河流域为研究区域,基于GIS(地理信息系统),利用L-THIA(long-term hydrologic impact assessment,长期水文影响评价)模型,基于2015年土地利用地图数据、土壤水文数据以及长时间序列(2009—2014年)逐日降雨数据,调整模型参数,使模型模拟径流量符合水文站监测数据,进而模拟2014—2015年流域内的非点源污染负荷空间分布.L-THIA模型模拟得到濑溪河流域径流量约为5.10×108m3,和控制水文站实测径流量相比,模型模拟相对误差为5%,表明模型模拟质量较好,模拟结果可信度较高.结果表明,流域内TP、NH3-N、CODCr非点源污染负荷分别为204.10、353.12、5 162.53 t;农业用地对研究区的非点源污染影响最大,林地最小;根据濑溪河水系分布特点将研究区划分为16个控制单元,各控制单元TP、NH3-N、CODCr的空间分布特征及比例相似,研究区非点源污染平均负荷强度为3.72 t/km2,TP、NH3-N、CODCr的输出范围分别为(0.08~0.15)(0.14~0.27)(2.19~3.89)t/km2.研究显示,流域非点源污染产生量的估算和空间分布特征的揭示为编制濑溪河流域水污染治理方案提供了科学参考.

The non-point source pollution is one of the most important contributors to water environment deterioration in river basins.Mastering the spatial and temporal distribution characteristics of non-point source pollution is a fundamental task of water environmental pollution control and integrate driver basin management.To implement the action plan for preventing and treatment of water environmental pollution issued by the State Council of China,Sichuan Province launched a comprehensive plan to improve the water environment in the major river basins such as the Laixi River.To explore the non-point source pollution load and its spatial distribution within the river basin is of importance for putting forward a scientific scheme for water environment improvement in the basin.Taking the Laixi River basin in Sichuan Province as the study area,with the support of GIS,a localized long-term hydrologic impact assessment(L-THIA)model was used to estimate the spatial distribution of non-point source pollution load.Based on land use map retrieved from remotely sensed images in 2015,soil hydrological data in 2015 and long time series data of the daily rainfall records from 2009 to 2014,the model parameters were adjusted.The model was validated based on the model simulation results and the monitoring data from the hydrological station in order to simulate the distribution of the non-point source pollution load in the watershed.The runoff volume simulated by the model is 5.10×10 8 m 3,which was consistent with the monitoring data of the hydrological station(5%error),and it indicates that the model simulation is of good performance.The results show that the annul non-point source pollution load of the total phosphorus(TP),the ammonia nitrogen(NH 3-N)and chemical oxygen demand(COD Cr)was 204.10,353.12 and 5162.53 t respectively.The agricultural land has the most important impact on non-point source pollution in the study area,and the woodland has the least influence.With the digital elevation model(DEM),the study area was further divided into 16 control units according to the river system characteristics.The spatial distribution characteristics of TP、NH 3-N、COD Cr and the proportion were found similar to each other.The average non-pointing source pollution loading intensity of the study area was 3.72 t km 2,output ranges of loading intensity of TP、NH 3-N and COD Cr were(0.08-0.15)(0.14-0.27)and(2.19-3.89)t km 2,respectively.The research shows that the results of this study can provide scientific reference for raising the water pollution control scheme in the Laixi River Basin.